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76,xxxg del ex e9 Enviado desde mi teléfono inteligente Sony Xperia™ ---- Anderson M. Winkler escribió ---- Hi Khoi, Please, see below: On 12 June 2016 at 05:43, Khôi Huỳnh Minh <[log in to unmask]> wrote: > Dear Anderson, > > Sorry for pull out this topic > again but I have a question that related to what I mentioned before. > > Is > the time series extracted from ICA have that characteristic of the > haemodynamic response ? I means we all know that BOLD signal can be model > by HRF and a set of stimulus and deconvolute BOLD signal with suitable > stimulus can give us HRF. How about for time series from ICA result. > We would hope so, yes, after unmixing, the time courses still represent BOLD responses, that could, potentially, be subjected to deconvolution. > > I have recorded the time seed when subjects in my experiment tap their > finger. I try to convolute this with HRF and find out that the result is > somewhat correlate with one IC time series (correlation about 0.3-0.4). The > spatial map of that IC show activation at motor cortex and frontal lobes. > Can we conclude that the spatial map is the activation map for the "finger > tapping" activities ? I doubt that by decompose fMRI signal into ICs, the > IC time series do not have haemodynamic response characteristic. > Yes, that sounds the right interpretation. However, given it is a task-based experiment, and given that you know the stimulus onsets, perhaps a more powerful and successful approach would be to use the GLM, as opposed to ICA. All the best, Anderson > > It would be appreciated if you can help me point out the problem as my > conclusion make me feel somewhat fallacious. > > Best regards, > > Khoi > > > On Fri, May 13, 2016 at 3:27 PM, Anderson M. Winkler < > [log in to unmask]> wrote: > >> Hi Khoi, >> >> I understand that the null hypothesis is that there is no pattern across >> subjects, thus the expected average across subjects would be a map of all >> zeroes. This doesn't seem a very good hypothesis from the outset, as we may >> expect that commonalities among timecourses would be enough to render the >> maps similar among them. Still, such a test can be done with unthresholded >> maps, concatenated (in standard space) and tested in randomise with the >> option -1. >> >> To make this a bit more objective, consider taking, for each component, >> the one that has the strongest correlation of timecourse with the stimulus >> function, even if such correlation is poor for some subjects. >> >> That said, perhaps better is to simply use the GLM: since you have >> already a sequence of stimulus, these can be used as the regressors in a >> 1st level, and the common pattern can be found in a higher level. There >> will be no risk for circularity whatsoever, and no issues related to the >> scaling of components (z-stat, etc). >> >> All the best, >> >> Anderson >> >> >> >> On 13 May 2016 at 04:34, SUBSCRIBE FSL Khoi Huynh <[log in to unmask]> >> wrote: >> >>> Dear FSL experts, >>> >>> After running single ICA for all subjects, I find that each subject has >>> 1 IC which its time series is highly correlated with my interest stimulus. >>> The stimulus design is not the same for all subject hence I cannot use >>> tensor ICA. I want to maintain as much as information possible so I dont >>> want to use concat ICA (since concat ICA will run in MNI space instead of >>> subject space). >>> >>> Here is what I got after my single ICA run: >>> -Time series of IC 1 of subject 1 is correlated with the event subject 1 >>> lost the game -> zstats_threshold map of IC1 - subject 1 >>> -Time series of IC 7 of subject 2 is correlated with the event subject 2 >>> lost the game -> zstats_threshold map of IC7 - subject 2 >>> .... so on. >>> >>> I registered all the zstats_threhold map to MNI space but then stuck at >>> finding a way to find common pattern of them. >>> Hence, is there any way in FSL that I can find common activation from >>> all of the zstats_threshold maps ? I am thinking of average all the map and >>> threshold the result at a specific threshold but I feel like it is not the >>> correct way. >>> >>> It would be very appreciated if anyone can give me any advice. >>> >>> Best regards, >>> Khoi >>> >> >> >